1. Field
The present disclosure is directed to multiplexing techniques and multiple access techniques.
2. Description of the Related Technology
Multiplexing techniques allow multiple signals to share a single physical channel. Traditional multiplexing techniques include time-division multiplexing (TDM), frequency-division multiplexing (FDM), and code-division multiplexing (CDM). CDM, which multiplexes multiple signals into the same time interval and frequency band by orthogonal codes, requires the original signals to be in the same domain (e.g., time or frequency). In a hybrid system, such as a hybrid orthogonal frequency-division multiplexing (OFDM) and cyclic prefix single carrier (CP-SC) system, the orthogonal signals are transmitted in different domains and traditional CDM cannot be utilized. Multiple access techniques allow signals from multiple users to be transmitted through a single physical medium. Traditional multiple access techniques include time-division multiple access (TDMA), frequency-division multiple access (FDMA) and code-division multiple access (CDMA). As a special case of FDMA, OFDMA (orthogonal frequency-division multiple access) allocates orthogonal sub-carriers among multiple users. In traditional OFDMA systems, a single sub-carrier is the smallest allocable unit which can be allocated to only one user.